Rotary power devices, also referred to as cylindrical energy modules (CEM) are described in the U.S. Pat. No. 5,209,190, granted May 11, 1993 to Eddie Paul. The CEM is a device capable of functioning as a highly efficient positive displacement pump, as a compressor or, with minor modifications, as an internal combustion engine. As a pump, the CEM is self priming and is capable of pumping both gases and liquids or combinations of liquid and gas which renders it highly suited for the production and pumping of foam, such as fire fighting foam.
It has been found, however, that in the manufacture of the CEM, tolerance between the end walls of the CEM housing forming the stator and the rotor assembly end walls is critical. If the tolerances are too close the rotor Assembly will seize up causing a complete malfunction of operation of the CEM. On the other hand, if the tolerances are to loose the efficiency of the CEM will be substantially reduced. Maintaining the proper clearance between the rotor assembly and the stator end walls requires highly skilled machining operations calling for extremely close tolerances which substantially increase the cost of manufacturing the CEM. Even where the machining tolerances are held, in has been found that occasionally during the operation of the CEM buildup of heat will cause the rotor assembly and the stator to expand resulting in galling of the cylinder heads and stator end walls or complete malfunction of the device due to seizing of the rotor assembly.